Gas treater



Sept. 17, 1940- c. w. J. HEDBERG Er Al.. 2,215,267

GAS TREATER Filed Nov. 22, 1938 2 Sheets-Sheer l I I I I I I I I I I IIIl/ f f/ llI\\ ///r\\|/(\\\\ l f f l\ //l /l|\ l l l I l Sept 17, 1940-c. w. J. HDBx-:RG ETAL 2,215,267

GAS TREATER Filed Nov. 22, 1938 2 `Sheets-Sheet 2.

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llllllll/lll/l/ll Patented Sept. 17, 1940 UNITED STATES PATENT OFFICEGAS TREATER New York Application November 22, 1938, Serial No. 241,862

3 Claims.

This invention relates to the electrical insulation of high potentialmembers in apparatus for the treatment of gases containing constituentscondensible to form electrically conductive,

corrosive, inflammable or otherwise troublesome substances. Theinvention is particularly applicable to electrical precipitators used incleaning hot phosphorus-containing gases such as are produced in theelectrothermic or blast furnace l reduction of phosphate materials.

A principal purpose of the invention is the provision of means for theeective electrical insulation of high potential members of apparatus fortreating gases containing condensible substances.

A further object of the inventio-n is to prevent the contamination ofliquid sealing substances used in electrical precpitators by condensiblecomponents of the gases being treated.

It has been found that these and other desirable objects and advantagesmay be attained by providing a liquid seal structure including a body oiinsulating liquid positioned to insulate electrically the high tensionmembers of a gas treatl5 ing apparatus 'from the low tension membersthereof and to prevent free flow of gas between the interior and theexterior of the apparatus and by providing means whereby the surface ofsaid body of liquid which communicates with the 0 interior of theapparatus may be flushed or screened by a stream of inert gas. It hasbeen found to be advantageous to provide also means whereby thetemperature of the protective gas and of the body of liquid may bedifferentially maintained.

When applying the invention to the cleaning of gases containing, forexample, phosphorus, it is particularly desirous that the flushing gasbe maintained at a temperature above the dew l0 point of any phosphorusthat may be contained therein or diffuse thereinto from the gases beingtreated. It is further desirable to maintain the sealing liquid at arelatively low temperature to reduce the solubility of phosphorus 15therein and the rate of diffusion of dissolved phosphorus therethrough.

For the purpose of illustration the invention will be more particularlydescribed as applied to ro an electrical precipitator for the cleaningof hot phosphorus-containing gases, with reference to the accompanyingdrawings in which:

Fig. l is an elevation in partial section of the upper portion of anelectrical precipitator em- 55 bodying the invention;

Fig. 2 is atop view in partial section of the precipitator of Fig. l;and

Fig. 3 is an enlarged fragmentary detail in elevation of a portion ofFig. 1.

In the drawings, numeral I0 designates the -5 shell of an electricalprecipitator having inlets I2 and outletsl I3. The shell is insulated asindicated at I4 and is divided into a downpass portion and an uppassportion by vertical partition I5. l0

Positioned over opening I6, in top plate II of shell I0, is oil seal I8.

The oil seal comprises an annular trough consisting of a cylindricalouter wall 20 welded at 22 to inner wall and bottom member 2l, and an 1Iapron 46 positioned so that the bottom rounded edge 41 of the apron issubmerged in the oil I9 within the annular trough. Wall 20 is surmountedwith a ring 26 to eliminate any tendency for discharge from the edge tomembers of 20 different potential. Member 2| is also surmounted with arounded member, in this instance a hollow torus ring 23. Apron 45 isformed as a cup which is suspended in inverted position from dischargeelectrode suspension member 50, being held to member 50 by clamp 48.

Beneath and inside trough member 2I is a hollow walled assemblycomprising annular members 28 and 29 with gas space 30 between them andheat insulation 38, preferably attached to $0 member 28, to heatinsulate member 28 from trough member 2l. This assembly is held inposition in cylinder 2G by spot welding at contact line 21 and alsowhere members 23 and 29 contact at 23. Gases are admitted to space 30 35through inlet connection 40. They leave space 30 through holes 33, whichpermit portions of the gases to issue directly into the annular spacearound member 50, and through holes 34 which permit other portions ofthe gases to pass through space 31 above insulation 38 through holes 35into ring 23 and thence through holes 25 in ring 23 to the spacedirectly over the oil I9. Oil is admitted to the seal through feed pipe4I, annular distributing pipe 42 and outlet noz- 45 zles 43. An outletpipe 44 carries the oil back to storage or to settling tanks or otherconditioning means (not shown), an overflow Weir 44 in pipe 44 beingused to maintain the oil in the seal at the desired height, and a valve44 be- 50 ing provided for the purpose of draining the seal.

Mounted on cylinder 20 of oil seal I8 is an oval-shaped insulatorcompartment with floor 56, side Wall and top 51. Two pedestal typeinsulators 60, resting on oor plate 56, support 55 a horizontalcomposite beam 6l which extends over oil seal iS and supports rod 50,xed collars 62 and 63 on rod 50 being used to maintain the rod in thedesired position. About each insulator Gil, is a conical shapedenclosure l0 with upper end open which is for the purpose of keeping anycondensible vapors which may evaporate from the outer portion of thesurface of oil i9, or other conducting material, from reaching thesurface of the insulator. A purging gas (clean, dry air, for example),is introduced from a suitable source (not shown) through pipe l2 intothe bottom of enclosure 70, annular pipe li with holes spaced about itstop surface and positioned about the base oi insulator 60 being used toliberate and distribute the gas within the enclosure. The high voltageelectrodes 53 hanging from members 52, which in turn are supported byframe work 5l and rod 50, are energized through a conductor which isintroduced through the center of insulator 60 and makes electricalcontact with beam Si. The collecting electrodes (not shown) and theshell of the precipitator are grounded as indicated at 85.

Mounted on top of rod 50 is a box Sl! containing rapping means operatedthrough a shaft 5l' by a mechanism (not shown) which is attached toiianged opening Held by couplings 55 on shaft 6l is an insulating linkmember 65 usually of electrical porcelain which insulates the ground endof shaft Si and the mechanism which turns it from box which is at high'potential, being in contact with rod Insulator is protected from foreignmatter by an enclosure in the same manner in which insulator isprotected, the piuging gas being supplied through pipe il to distributorlli. Enclosures 'ifi and are made in halves can be pulled apart when theinsulators are to be inspected and cleaned. The

insulator compartment can be entered t'L 'ough eas outlet lf3 withdamper ill manholes Sil. A L controls the gas pressure within theinsulator compartment.

The precipitator embodying the invention is operated as follows whengases carrying phosphorus vapors are to be cleaned as they leave thefurnace at about 230 C. (4A-6 E). The shell and contents oi theprecipitator heated, preferably by surface heating ur ts, to atemperature above the phosphorus dew point oi the gases. rThe phosphorusdew point is usually about 180 C. (356 FJ, and the precipitator iscommonly heated to slightly over 200 C. before the gases to be cleanedare turned into it. Before or while the precipitator is being heated itis purged with a non-combustible gas such as carbon dioxide.

The insulator compartment is not heated to as high a temperature as theremainder of the precipitator because the oil seal prevents the gasesfrom circulating into and. permitting phosphorus vapors to condense inthat part of the precipitator. Clean air, at a temperature well aboveits dew peint, is introduced through pipes 'l2 and 'll to gas ushinsulators G0 and respectively. This air escapes through opening 85,although other openings can be provided.

When the furnace gases are introduced into the precipitator, it isadvisable to simultaneously introduced heated carbon dioxide or othergas, which is relatively inert to both phosphorus and its carrying gas,into the oil seal through pipe 40. This gas is preferably heatedindirectly with high pressure steam or by electric heaters to about 160to 180 C. After the furnace gases are cleaned in the precipitator andcooled in condensers and the phosphorus removed, they may be reheatedand used as purge gases on the interior surface side of the oil seal.The use of carbon dioxide is then discontinued. Some phosphorus vapormay remain in the gases, which comprise principally carbon monoxide,returned from the phosphorus condensers but it is in such small amountsthat the phosphorus dew point will in general be below 70 C. The purgegas must be heated to above its phosphorus dew point but it need not beheated to the phosphorus dew point of the raw furnace gases. With steamat pounds per square inch, the returned gases for purging can be heatedto about 150 C. and this has been found to be a very satisfactorytemperature for those gases.

The temperature drops through the precipitator are, in an illustrativeexample, as follows: Raw gas to be cleaned, 230; purging gas iiowinginto oil seal, 150; oil leaving oil seal, 90; and air in insulatorcompartment, about 40 C. These controlled temperature drops keep allgases containing phosphorus above their phosphorus dew points,respectively, keeps the oil well below its flash point, which may bebetween and C., and keeps the air or gas in the insulator compartment inmotion and at a temperature which minimizes evaporation of phosphorusfrom the oil and condensation of that phosphorus on insulating surfaces.

We claim:

l. In the electrical treatment of gases containing a readily condensiblecomponent, the improvement which comprises providing an insulatingliquid seal between the high tension and the low tension portions of thetreating apparatus having a free liquid surface in communication withthe interior of the treating apparatus, directing a current of an inertgas maintained at a temperature above the dew point of the condensiblecomponent of said flushing gas over the interior surface of the sealingliquid, and maintaining the sealing liquid at a substantially lowertemperature than that of the ushing gas.

2. in the electrical treatment of gases containing phosphorus theimprovement which comprises providing an insulating liquid seal betweenthe high tension and the low tension portions of the treating apparatushaving a free liquid surface in communication with the interior of thetreating apparatus, directing a current of an inert gas maintained at atemperature above the phosphorus dew point of said ilushing gas over theinterior surface of the sealing liquid and maintaining the sealingliquid at a substantially lower temperature than that of the ushing gas.

3. In the electrical treatment oi gases containing phosphorus, theimprovement which comprises providing an insulating liquid seal betweenthe high tension and the low tension portions of the treating apparatushaving a free liquid surface in communication with the interior of thetreating apparatus, and directing a current of an inert gas maintainedat a temperature above the phosphorus dew point of said flushing gas outbelow the phosphorus dew point of the gas being treated over theinterior surface of the sealing liquid.

CARL W. J. HEDBERG. LOUIS N. BONACCI.

